Customers with no recent orders?

[Brian Dunning]

I thought I could find the answer to this by googling, but had no luck.

How do I show a list of customers who:
(a) Have placed no orders within 14 days,
(b) Have been a customer for at least 14 days. (They do not have to  
have placed any orders, ever, to be a customer.)

I'm trying to show inactive customers, but I don't want to include  
someone who only joined the customer list recently and has not yet had  
time to place any orders.